Dependence Of Viscosity Research Articles

A method for rheological measurements of air sensitive samples.

The rheology of air or moisture sensitive liquids, gels, and glasses requires complicated rheometer-in-glovebox laboratory setups. Here, we demonstrate the use of a heavier-than-air cover gas, sulfur hexafluoride, and the design of a cover gas container that can attach to the lower geometry plate of any rheometer to carry out rheology experiments on air-sensitive liquids and soft solids. Rheological measurements of air-reactive ionic liquid trimethylsulfonium bromide-AlCl3, moisture sensitive titanium(IV) propoxide, and glycerin demonstrate the effectiveness of the cover-gas method for loading samples on acquiring correct temperature dependent viscosity data of the sample in the absence of reaction products.

Viscosity Anomalies of Magnetic Fluid Stabilized by a Double Layer of Surfactant in Water

Purpose to study the temperature dependence of the viscosity of a water-based magnetic fluid.Method. Consists of measuring the dynamic viscosity of a magnetic fluid based on cobalt ferrite particles stabilized in water by a double layer of surfactant. Lauric acid (first layer) and a mixture of lauric acid and sodium dodecyl sulfate (second layer) were used as a stabilizer. Measurements were performed using a Brookfield DV-II+Pro rotational viscometer equipped with a coaxial cylinder system. The measuring system of the viscometer was thermostated using a KRIO-VT-12-1 thermostat.Results. The temperature dependences of dynamic viscosity were measured for three samples of magnetic fluid based on cobalt ferrite particles of various concentrations in the temperature range 0–90C°. The obtained temperature dependences of viscosity are radically different from the temperature dependences both predicted by known theories and experimentally observed for kerosene-based magnetic fluids. According to well-known theoretical models, the ratio of the viscosity of the magnetic fluid to the viscosity of the base medium is a certain universal function of particle concentration. Different models offer different types of this feature. But it clearly follows from them that the viscosity ratio should not depend on temperature. For magnetic fluids based on kerosene, it has been experimentally established that its relative viscosity decreases with increasing temperature. However, according to the results obtained, the relative viscosity of a water-based magnetic fluid does not decrease with increasing temperature, but increases significantly. That is, the viscosity of a water-based magnetic fluid decreases more slowly with increasing temperature than the viscosity of water.Conclusion. The observed dependencies completely contradict the known patterns, both theoretical and experimentally established for kerosene-based magnetic fluids. The results obtained may be useful for the further development of the theory of aqueous colloidal solutions with particle stabilization by a double layer of surfactants.

SLAG—software for reconstruction of historical smelting processes based on slag properties

AbstractThe publication presents the functions of the SLAG software created to recreate historical metallurgical processes. SLAG allows for determining the smelting temperature, the viscosity of the metallurgical melt, and the oxygen and sulfur fugacities during smelting. With software, both liquidus temperature and melt viscosity can be calculated using different models, covering the range of chemical compositions of historical slags as wide as possible. Based on thermodynamic calculations, SLAG allows the performance of O2 and S2 fugacity calculations in the temperature range of 1000–2000 K (727–1727°C). The range of applicability of other properties (viscosity and liquidus temperature) depends only on the limitations of individual models. Using SLAG, it is also possible to create predominance area diagrams (PADs) and diagrams that consider the viscosity's dependence on temperature for slag of a given chemical composition. Based on glass transition temperature (Tg) and melt fragility, it is also possible to reconstruct the conditions that prevailed during the various stages of historical glass manufacturing processes.

A Numerical Study of the Influence of Temperature Dependent Viscosity and Prandtl Number on Unsteady Natural Convection Flow of Methanol Over a Sphere with Magnetic Field

A Numerical Study of the Influence of Temperature Dependent Viscosity and Prandtl Number on Unsteady Natural Convection Flow of Methanol Over a Sphere with Magnetic Field

Effects of a typical shear dependent viscosity on analytical elastohydrodynamic lubrication film thickness predictions: A critical issue for the classical approach

Many engineering estimates of the film thickness in the concentrated contacts of real machines have come from extrapolations of measurements of elastohydrodynamic lubrication film thickness performed in glass on steel elastohydrodynamic rigs. Such estimates are likely to have large errors due to shear dependence of viscosity. The classical film thickness formulas employed have not been validated except for some Newtonian reference liquids at room temperature because the real pressure-viscosity response measured in viscometers has been ignored. A blend of polyalpha olefin base oils with mild shear-thinning has been employed in a line contact calculation to assess the effects of shear-dependent viscosity on the power-law exponents of the classical film thickness formula. The exponents on the pressure-viscosity coefficient and on the elastic modulus of the solids are not sensitive to the non-Newtonian effect. The exponents on ambient pressure viscosity and velocity are slightly reduced by shear-thinning. The exponents on pressure and scale are substantially increased by the shear dependence. The usual practice of measuring film thickness in an elastohydrodynamic rig to obtain an effective “[Formula: see text]-value” to use in a classical Newtonian film thickness formula will overstated the film thickness of a liquid which is shear dependent in the elastohydrodynamic lubrication inlet.

Effect of parameters-dependent viscosity and thermal conductivity on the thermo-hydraulic performance of Al2O3-based nanofluids in a rectangular microchannel

The multi-parameter dependence of nanofluid viscosity and thermal conductivity on the flow and heat transmission properties of Al2O3-H2O nanofluidin microchannels is investigated in this paper using a numerical simulation approach, exploring the effects of various parameters on flow and heat dissipation characteristics, such as flow velocity, pressure drop, temperature, and heat transfer coefficient, under different Reynolds numbers, etc. These parameters include the nanoparticles phericity (0.5~1.0), volume fraction (0.6%~6.0%), and temperature (290K~370K) of the nanofluids, as well as the boundary parameter Reynolds number (200~1000). The results show that the multi-parameter dependence of nanofluid viscosity and thermal conductivity setting has a significant impact on the flow and heat dissipation characteristics of nanofluids, comparing analysis with the nanofluid viscosity and thermal conductivity only related to the volume fraction under the same condition. Under the combined action of sphericity, volume fraction, and temperature, increasing the sphericity increases the pressure drop and decreases the heat transfer coefficient. For example, at a Reynolds number of 1000, the maximum rates of change for pressure drop and heat transfer coefficient are 0.85 and 4.26, respectively. The nanofluid thermo-hydraulic performance is sensitive to temperature, volume fraction and sphericity in turn. Setting up viscosity and thermal conductivity equations with multiple parameter dependencies can provide more accurate results for there search of nanofluids, further deepening the application research of nanofluids.

РАЗРАБОТКА ПРОГРАММНОГО ОБЕСПЕЧЕНИЯ МОДЕЛИРОВАНИЯ ПРОЦЕССОВ ТЕПЛОМАССОПЕРЕНОСА ПРИ МНОГОФАЗНОМ ПОТОКЕ

Mathematical models simulating the process of heat and mass transfer in a multiphase flow and taking into account the thermal conductivity of the working fluid, taking into account its location in space, physical properties and other characteristics, are difficult to implement in the form of software. Usually such models are represented by nonlinear equations, which makes it difficult to implement them correctly using numerical methods. When developing such mathematical models, hydrodynamics, heat transfer of a moving working fluid and the dependence of viscosity on temperature and velocity gradient are not taken into account. (Research purpose) The research purpose is developing a mathematical model of the functioning of the heat supply system as a set of cylindrical pipelines with a heat source through which the working fluid moves. Additional conditions are introduced to achieve high accuracy of calculations at boundary points. The possibility of using analytical equations to calculate the internal heat dissipation during the transportation of the working fluid inside the pipeline is studied. (Materials and methods) Using the two-phase delay theory (DPL-model) and the finite element method (FEM) as flow balancing methods, we obtain a model of the heat exchange of the working fluid motion in the pipeline with the possibility of taking into account relaxation properties. (Results and discussion) The developed algorithm is implemented using the high-level interpreted programming language MATLAB and its simulation environment for complex technical systems Simulink. (Conclusions) Equations modeling the real motion of a multiphase working fluid in locally nonequilibrium systems, including heat supply systems, are obtained. The results obtained make it possible to compile an algorithm and implement it using the high-level interpreted programming language MATLAB, defining a working version of the software for modeling heat and mass transfer processes in a multiphase flow.

High magnetization composite magnetic fluid: structure, magnetorheology and new sealing mechanism in rotating seals.

The sealing capacity of magnetofluidic (MF) rotating seals is limited by the highest magnetization of the sealing ferrofluids (FFs) of about 1000 G (80 kA m-1). A sharp, almost an order of magnitude, increase in the supported pressure drop is possible by using a magnetorheological (MR) suspension as sealing fluid, owing to the much higher saturation magnetization of MR fluids compared to FFs. However, rotating seals with MR fluids have several shortcomings, such as a significant increase of the friction torque due to the growth of shear stress in the strong magnetic field specific to MF seals and leakage of the non-magnetic carrier liquid. At least partly, these issues can be avoided by using ferrofluid based extremely bidisperse MR suspensions of micrometer-sized iron (Fe) particles dispersed in a ferrofluid, as sealing fluid. The composite Fe3O4-Fe magnetic fluid used in this study consisted of hundreds of nanometers up to few microns size structures of interconnected (welded) Fe nanoparticles (FeMNPs) dispersed in a high colloidal stability ferrofluid with 500 G (40 kA m-1) saturation magnetization. The volume fraction of iron NPs varies from 0.5 to 15% in the ferrofluid carrier which significantly increases the magnetization and simultaneously produces important changes of flow properties in magnetic field of the resulting composite fluid, from Newtonian to strongly non-Newtonian behavior. The evaluation of the magnetic and magnetorheological behavior includes the dependence of magnetization, effective viscosity, magnetoviscous effect and dynamic yield stress on the volume fraction of Fe nanoparticles dispersed in the ferrofluid carrier. The seal gap filled with interconnected Fe nanospheres consists in randomly distributed microregions with a high intensity and high gradient magnetic field that captures the ferrofluid and provides a new sealing mechanism. Already a small amount of interconnected Fe nanospheres additive (2.5-5.0% volume fraction) produces four times increase of the rotating seal burst pressure, a much higher increase than what can be obtained from using a conventional magnetic fluid with the same magnetization. The nano-composite sealing magnetic fluid proved to be a cost-effective solution to significantly increase the performance of multi-stage rotating MF seals.

ВЛИЯНИЕ ЭКСТРАКТИВНЫХ АГЕНТОВ НА ПЛОТНОСТЬ И ВЯЗКОСТЬ ЖИДКОЙ ФАЗЫ ПРИ РЕКТИФИКАЦИИ СМЕСИ ИЗОПРОПАНОЛ-ВОДА

In this work, the dynamic viscosity and density of three-component mixtures consisting of a binary azeotropic mixture of isopropanol-water and an extractive agent were investigated. Three points of the profile of concentrations in the liquid phase in the extractive separation column of isopropanol-water mixture in recalculation on the pseudobinary mixture were selected for research: the first point - 95/5 % wt. %; the second point - 5/95 % wt. %; the third azeotrope point - 88/12 % wt. %. For the selected points model mixtures were prepared to which 13 % wt. % of the extractive agent was added. The extractants used in this work were monoethylene glycol (EG), which is used in industrial processes, 1-ethyl-3-methyl imidazolium chloride ([Emim][Cl]) and triethylene glycol-based boronic acid amino ester (AEBA). Experimental data on concentration and temperature dependences of dynamic viscosity and density were obtained for these mixtures. The results showed that the viscosity of the system increases in the series of EG, AEBA, [Emim][Cl]. To carry out calculations of the investigated thermophysical properties in the work we used known expressions: for density - through the sum of volumes; for viscosity - the Kendall-Manroe model. For a three-component mixture with EG, the results of calculations of properties performed in the AspenPlus V12 package are presented. The studies carried out in this work have shown that the density modeling of the studied mixtures is quite accurate, the discrepancy between experimental and calculated data does not exceed 1%. Modeling of the dynamic viscosity coefficient of the system by the Kendall-Manroe model for isopropanol-water mixture in the presence of the studied extractive agents can lead to significant errors, the maximum value reaches 52%. The calculated values of the dynamic viscosity coefficient are underestimated, which in turn can lead to errors in modeling (on the basis of these properties) of heat and mass transfer processes occurring in the apparatus.

Modeling of stationary mode for pipeline operation during hot oil pumping

The objective of this work is to build and analyze a mathematical model of steady-state operation of a pipeline that conducts hot oil pumping in a particular section. Mathematical modeling of pipeline operation during hot pumping makes it possible to determine the pumping flow rate, temperature and pressure distribution along the length of the pipeline. The object and subject of the study is a horizontal pipeline route between two pumping stations with preheating of oil at the beginning of the section. Within the framework of this work, the dependence of oil viscosity on temperature was determined, and the following graphs were obtained: graph of oil temperature distribution in the considered pipeline section, graph of pressure distribution in the pipeline in the considered section, graph of hydraulic resistance coefficient distribution according to the Leibenzon model, graph of pressure distribution in the pipeline in the considered section according to the combined model of Shukhov and Leibenzon. The graphs obtained allowed us to assert that taking into account the real rheological properties of oil leads to a change in the law of pressure distribution along the pipeline route and to a significant change in the length of the linear section of the pipeline, where a significant pressure drop occurs.

Modeling of stationary mode for pipeline operation during hot oil pumping

The objective of this work is to build and analyze a mathematical model of steady-state operation of a pipeline that conducts hot oil pumping in a particular section. Mathematical modeling of pipeline operation during hot pumping makes it possible to determine the pumping flow rate, temperature and pressure distribution along the length of the pipeline. The object and subject of the study is a horizontal pipeline route between two pumping stations with preheating of oil at the beginning of the section. Within the framework of this work, the dependence of oil viscosity on temperature was determined, and the following graphs were obtained: graph of oil temperature distribution in the considered pipeline section, graph of pressure distribution in the pipeline in the considered section, graph of hydraulic resistance coefficient distribution according to the Leibenzon model, graph of pressure distribution in the pipeline in the considered section according to the combined model of Shukhov and Leibenzon. The graphs obtained allowed us to assert that taking into account the real rheological properties of oil leads to a change in the law of pressure distribution along the pipeline route and to a significant change in the length of the linear section of the pipeline, where a significant pressure drop occurs.

Magnetohydrodynamic Conjugate Free Convective Heat Transfer Analysis of an Isothermal Horizontal Circular Cylinder with Temperature Dependent Viscosity

Magnetohydrodynamic Conjugate Free Convective Heat Transfer Analysis of an Isothermal Horizontal Circular Cylinder with Temperature Dependent Viscosity

Formation of the Naxos nested domes and crustal differentiation by convection and diapirism

The Naxos dome, in the middle of the Aegean domain, exposes the former root of the Alpine orogenic belt and represents a key natural example to investigate the development of gravitational instabilities during orogenic evolution and their impact on crustal differentiation. The Naxos dome is cored by migmatites with structures depicting second order domes with a diameter of 1–2 km nested in the first order deca-kilometer scale dome that formed at the onset of orogenic collapse. Zircon grains from the migmatites record a succession of crystallization-dissolution cycles with a period of 1–2 Myr. These features have been attributed to the development of convective and diapiric gravitational instabilities, related to thermally induced and compositional buoyancy. In this paper, we test the pertinence of this model with a thermal-mechanical numerical experiment performed with a volume of fluid method (VOF) known to preserve material phase interfaces during large deformation of viscous layers. Partial melting of the crust is modeled by strain-rate and temperature dependent viscosity and temperature dependent density. Moreover, horizontal layers with density, viscosity and heat production variations mimic more felsic or more mafic lithologies in a crust of intermediate composition. With basal heating, gravitational instabilities initiate with local segregation of the buoyant versus heavier layers, followed by diapiric upwelling of buoyant pockets of aggregated less dense material. Convection starts after 5 Myr, approximately when half of the crust has a viscosity lower than 1019 Pa s. The size of the convection cells increases as the temperature rises in the crust and reaches ∼25 km in diameter after ca. 20 Myr, which defines the size of first order domes. Some of the heterogeneous material is entrained in the convection cells with a revolution period of 1 to 3 Myr. However, most of the denser material accumulates in the lower crust, while the buoyant material segregates at the top of the convection cells and forms diapirs that correspond to second order domes, of several kilometers in diameter and nested within the first order domes. This model, which reproduces the first order characteristic dimensions of the Naxos nested domes and the periodicity of their zircon geochronological record, demonstrates the efficiency of gravitational instabilities in the formation of migmatite domes and, more generally, in the multi-scale dynamics of crustal differentiation leading to a felsic upper crust, an intermediate middle crust and a mafic lower crust.

Solution properties of laccase-treated pectic polysaccharides derived from steam-dried sugar beet pulp

Steam-drying of sugar beet pulp enables hot water extraction of pectic polysaccharides without adding acid to the extraction medium with a yield higher than the conventional preparation method but a lower molecular weight. The objective of the present study was to investigate the effect of laccase treatment on the molecular weight and solution properties of the pectic polysaccharides derived from steam-dried sugar beet pulp using hot water extraction. The weight average molecular weight and intrinsic viscosity of the pectic polysaccharides increased from 97.1 kDa to 147 kDa and from 0.383 dL/g to 0.525 dL/g due to isopropanol fractionation to remove low molecular weight fractions, respectively, and then to 661 kDa and 0.832 dL/g by the laccase treatment at the highest laccase rate examined, respectively. The intrinsic viscosity values showed a power-law relationship with the molecular weight, the exponent value of which was found to be 0.32 prior to the isopropanol fractionation or 0.38 after the isopropanol fractionation. These values were much lower than that derived theoretically for a random coil (0.5) and closer to that for a sphere (0.33). Compared to the results previously reported for various polysaccharides, the concentration dependence of the specific viscosity in the semi-dilute region was weaker, the critical concentration which is the threshold between dilute and semi-dilute solutions was higher, and the so-called coil overlap parameter was lower. The present results indicate that the pectic polysaccharides examined in this study had highly branched, compact, and spherical molecular structure.

Densities, viscosities, and refractive indices of binary mixtures of tri-n-butyl phosphate with propan-2-ol and butan-2-ol at 303.15, 308.15, 313.15, 318.15, and 323.15 K

Densities, viscosities, and refractive indices of binary liquid mixtures of tri-n-butyl phosphate (TBP) with propan-2-ol and butan-2-ol at different temperatures between 303.15 and 323.15 K at an interval of 5 K and across the entire range of composition were measured. The data were used to calculate derived properties, such as excess molar volumes, excess thermal expansivities, deviations in viscosities, excess free energies of activation for viscous flow, and deviations in refractive index. The variation patterns of these properties concerning composition and temperature for the propan-2-ol + and butan-2-ol + TBP systems were discussed and attributed to probable intermolecular hydrogen bonding and geometric effects. Notably, the influence of hydrogen bonding was substantial, as evidenced by trends in excess molar volumes and deviations in viscosities. Concentration-dependent polynomial equations were used to fit the measured data of density, viscosity, and refractive index, while Redlich-Kister-type equations were applied for the excess properties. The densities and viscosities were correlated using the Jouyban-Acree model. The correlating abilities of various models, such as Grunberg-Nissan, Tamura-Kurata, Heric, Ausländer, McAllister-3, and McAllister-4 body models, were also evaluated using the viscosity data. Additionally, six new pairs of UNIFAC-VISCO group interaction parameters were computed to predict viscosities of TBP in systems involving alkanes, aromatics, and alcohols, extending the application range of the group contribution model.

On the Shear-Thinning of Alkanes

The approximate power law dependence of the apparent viscosity of liquids on shear rate is often argued to arise from a distribution of energy barriers. However, recent work on the Prandtl model, which consists of a point mass being dragged by a damped, harmonic spring past a sinusoidal potential, revealed a similar dependence of the friction on velocity as that of many liquids. Here, we demonstrate that this correlation is not only qualitative but can also be made quantitative over a broad temperature range using merely three dimensionless parameters, at least for alkanes, in particular n-hexadecane, at elevated pressure p. These and other observations made on our all-atom alkane simulations at elevated pressure point to the existence of an elementary instability causing shear-thinning. In addition, the equilibrium viscosity shows power law dependence on p near the cavitation pressure but an exponential dependence at large p, while the additional parameter(s) in the Carreau–Yasuda equation compared to other rheological models turn out justifiable.

Anomalous Concentration Dependence of Viscosity: Hidden Role of Cross-Correlations in Aqueous Electrolyte Solutions.

The viscosity of aqueous electrolyte solutions exhibits well-known composition-dependent anomalies that show certain definitive trends and universal features. The viscosity of LiCl and NaCl solutions increases with concentration in a monotonic fashion, while solutions of KCl, RbCl, and CsCl exhibit a more complex behavior. Here, the viscosity first decreases and then increases with increasing concentration, with a rather broad minimum at intermediate concentrations (ca. 1-3 m). To unearth the origin of such puzzling behavior, we carried out detailed molecular-level analyses by interrogating the exact Green-Kubo expression of viscosity in terms of the stress-stress time correlation function (SS-TCF). The total SS-TCF can be decomposed into a collection of three self- and three cross-SS-TCFs arising from the three constituent components (water, cations, and anions). Mode coupling theory (MCT) analysis for the friction on ions and the viscosity of the solution suggests the possible importance of two-particle static and time-dependent cross-correlations between water and the ions. We calculate the viscosity and other dynamical properties for all five electrolyte (LiCl, NaCl, KCl, RbCl, and CsCl) solutions over a range of concentrations, using two models of water (SPC/E and TIP4P/2005). The total viscosity derives non-negligible contributions from all of the terms. The cross-correlations are found to be surprisingly large and seen to play a hidden role in the concentration dependence. However, the importance of cross-correlations is often not discussed. Our study leads to a theoretical understanding of the microscopic origin of the observed anomalies in the composition dependence of viscosity across all five electrolytes.

Optimization of Arabinogalactan Sulfation in Process Scaling

To ensure the safety of the arabinogalactan sulfation process, the thermal effect of the reaction (148.26 kJ) was determined by the thermal flux balance method. The dependence of the dynamic viscosity of the reaction medium on the way of introducing the sulfating agent and on its particle size was studied by phase rheology. The stirring process was calculated to substantiate the optimum stirrer design and determine the quality parameters of stirring of the reaction medium. The data obtained allow optimization of the process for producing Agsular® substance in scaling of the production technology.

Phase Transitions in Oil Disperse Systems and their Influence on the Thermochemical Process of Oil Dehydration

It is established that within the temperature range of oil dehydration in the fields, a phase transition occurs in oils, accompanied by a multifold change in the particle size of their dispersed phase. The study examines the method of assessing the temperature T* at which this process occurs based on the temperature dependence of oil viscosity. It is found that with T>T*, there are two effects taking place in oils that change the stability of oil-water emulsions in two opposite directions. Specifically, the reduction of oil viscosity facilitates a decrease in emulsion stability. In turn, increased emulsion stability is promoted by a rise in the content of natural emulsifiers in the oil disperse medium at T>T* due to a phase transition with a dramatic change in the particle size of the disperse phase. Therefore, the maximum speed and degree of oil dehydration is achieved at T*, which is confirmed experimentally. As a result, the need for a critical analysis of the oil treatment temperature regime used in the fields considering phase transitions within the particles of its dispersed phase is shown.

Oscillation Dynamics of Dielectric Polymer Droplets during Electrohydrodynamic Jetting in a Wide Range of Viscosities.

The electrohydrodynamic (EHD) jetting of fluids is used for several applications such as inkjet printing, atomization of analyte in mass spectrometry, liquid metal alloy ion sources, and electrospinning of polymer fibers. Historically, the bulk of research has focused on nonviscous, highly conductive fluids which are most suitable for EHD spray and printing, while there is relatively little experimental work on EHD jetting of highly viscous liquid dielectrics. We studied the dynamics of oscillation and pulsating jetting from a suspended drop of polydimethylsiloxane (PDMS) polymers in an electric field, with particular attention to the viscosity dependence of the oscillation period and meniscus elongation and contraction time over a wide viscosity range (102-105 cSt). The reported results could help the appropriate design of EHD processes and may open new possibilities for the rheological characterization of liquid polymers using small volumes at the scale of nanoliters.